国家天文台“GTC课堂”

Title: Kinematics of the Diffuse Intragroup/Intracluster Light in Groups and Clusters of Galaxies in the Local Universe

Abstract: Nearly all intragroup (IGL) and intracluster light (ICL) comes from stars which once were formed in galaxies but now they are not bound to any of them. In this talk I shall focus on the physical properties - phase space distribution, metallicity and age - of the ICL and IGL stellar component of the local clusters/groups, within 100 Mpc distance. Kinematic information on these very low surface brightness structures mostly comes from discrete tracers such as planetary nebulae and globular clusters, showing highly unrelaxed velocity distributions.  Cosmological hydrodynamical simulations provide key predictions for the dynamical state of IGL and ICL and find that most intracluster stars are dissolved from galaxies that subsequently merge with the central galaxy. The increase of the measured velocity dispersion with radius in the outer halos of bright galaxies is a key feature to identify IGL and ICL components. In the local groups and clusters, IGL and ICL are located in the densest regions, and their light fractions are few to ten percent, significantly lower than the average values in more evolved clusters. The IGL/ICL light shines from mostly old (~10 Gyr) and metal-poor stars ([M/Fe] < –1.0). The new imaging facilities, like LSST, Euclid, E-ELT and JWST, will greatly increase our knowledge of IGL/ICL and their progenitors, thereby increasing our understanding of this enigmatic component.

Biography:  Dr Magda Arnaboldi obtained her PhD at the International School for Advanced Studies (SISSA) in Trieste, Italy in 1992.  From 1993 to 1997, she was a postdoc and then research fellow at MT Stromlo Observatory, Australia.  From 1997 to 2005, she held research positions at the Italian National Institute of Astrophysics (INAF) at the Observatory of Turin and Capodimonte.  In 2005, she joined European Southern Observatory (ESO), where she is now Head of the Archive Science Group and full Astronomer of the ESO faculty.  Dr Arnaboldi is one of the world’s leading astrophysicists in extragalactic astronomy.  Her main contribution to this area includes 1) discovery and characterization of the physical status of diffuse light and halos in massive galaxies in the nearby universe and 2) the use of planetary nebulae (PNe) as kinematical tracers.  She established extragalactic PNe as tracers of light and motions in the most distant outskirts of galaxies. Thanks to her scientific efforts, extragalactic PNe are now a firm discussion topic in the IAU Symposia.

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